1. Field of the Invention
The present invention relates generally to a CDMA (Code Division Multiple Access) mobile communication system, and in particular, to a device and method for transmitting and receiving data according to a radio link protocol (RLP) used for effective data transmission in radio environments.
2. Description of the Related Art
In general, a CDMA mobile communication system has developed from the IS-95 standard which mainly provides a voice service into the CDMA-2000 standard which provides a high-speed data service as well as the voice service. The CDMA-2000 standard can provide high-quality voice service, moving picture service and Internet search service.
FIG. 1 shows an exemplary packet data service defined by the CDMA-2000 standard. In FIG. 1, a mobile station (MS) includes a terminal equipment (TE) and a mobile termination (MT). A base station is represented by BSIMSC (Base Station/Mobile Switching Center), and an interworking function block for connecting the BS/MSC to a data network (e.g., Internet), represented by IWF. The IWF block is a device for converting protocols from one to another, when different protocols are used. In FIG. 1, the upper service (or Web service) processors of the mobile station and the IWF block exchange data through a network protocol (or Internet protocol (IP)) processor and a link protocol (or point-to-point protocol (PPP)) processor. That is, the data assembled by the upper service processors is finally transmitted to the lower layers in the form of the link protocol packet, and the lower layers transmit the data using a proper protocol.
FIG. 1 shows an example where an EIA-232 controller is used between the TE and the MT. The link protocol packets transmitted to the MT through the EIA-232 controller are distributed to radio link protocol (RLP) frames through the RLP according to the present invention. Such generated RLP frame is transmitted over a physical channel connected according to the IS-2000 standard which is the CDMA-2000 standard. The RLP packets received at the base station over the connected physical channel are restored back to the link protocol packets and the restored packets are transmitted to the IWF block through the relay layer. In general, interfacing between the base station and the IWF block is performed according to the IS-658 standard. The IWF block reads data from the link protocol packets and transmits the data to the network protocol processor, and the data is finally transmitted to the upper service processor.
Although a description has been made of a process for transmitting data from the mobile station to the base station, the process for transmitting the data from the base station to the mobile station can be performed similarly. To provide various services, the CDMA-2000 standard supports various schemes different from that of FIG. 1. However, they have a common feature that the link protocol packets with the upper service data are transmitted over the radio physical channel through the RLP.
The RLP Type-3 specification generates only the RLP frame having a size proper to fill a physical channel frame of 9.6 Kbsp or 19.2 Kbps for the current Rate Set 1, or the RLP frame having a size proper to fill a physical channel frame of 14.4 Kbps or 28.8 Kbps for the Rate Set 2. Therefore, when the physical channel operates at the higher rate of 153.6 Kbps or 230.4 Kbsp, there is used a method for filling several RLP frames in one physical channel frame. If the physical channel supports the rate of over 153.6 or 230.4 Kbps which is the maximum rate supported in the RLP Type-3 specification, for example, if the physical channel supports the rates of 307.2 Kbps, 460.8 Kbps, 614.4 Kbps and 1036.8 Kbps, more RLP frames can be filled in one physical channel frame. However, as compared with the method for filling one physical channel with one large-sized RLP frame, this method causes an increase in a burden on the frame header and unusable parts of the frame, thereby decreasing the frame efficiency. Therefore, to transmit the RLP frame having the size larger than the current RLP Type-3 frame, a new method is required.